This invention relates to an engine power management system for an aircraft, and more particularly to an electronic control system having a mechanical backup with particular advantageous features.
A recent advance in engine control technology for turbine engined light helicopters is the use of single channel Full Authority Digital Engine Control (FADEC) systems to automatically electronically control the fuel flow and engine speed throughout the entire flight regime. Such controls easily enable a single pilot to manage the complex task of flying a helicopter with one hand with a high degree of safety and reliability. However, on occasion such electronic systems fail, or for some other reason it is desirable to operate the engine or engines under manual control. Accordingly, it has recently become known to employ a manual backup system for electively controlling the helicopter engine, which is activated by means of twist grips rotationally affixed to the collective pitch stick. Such an advantageous arrangement enables the pilot to operate the engine controls with one hand (preferably the left hand) and to not have to perform contortions with both hands to start, stop, and operate the engines during flight, all while keeping the left hand on the collective pitch stick and the right hand on the cyclic pitch stick. The arrangement also keeps the pilot's hands on the control sticks in flight, and requires only a short movement of the left hand away from the collective stick to start or stop the engine at the beginning and end of a flight. Full engine control is enabled in either the fully automatic mode or the manually controlled backup mode.
The twist grips which have been employed in prior art systems have an arc of travel which includes an OFF position, a range in which the engine is under manual control, an IDLE position, and a full open position in which the engine is under automatic control. To take manual control of the engine under that scheme, the pilot must retard must retard the twist grip (or Power Lever) to the IDLE position, remove his/her hand from the collective control stick, reach to the console to operate an automatic-to-manual switch, reach back again to the twist grip, and then advance the twist grip to achieve the desired engine power.